1. Field of the Invention
The present invention relates to a multi-point autofocus system which can determine a focus state at each of a plurality of focus detection zones, and which is suitable for an optical instrument such as a camera.
2. Description of the Prior Art
In recent years, cameras provided with a multi-point autofocus system for determining a focus state (defocus) at each of a plurality of focus detection zones (focusing points) have been developed. In a camera having such a multi-point autofocus system, for instance, a plurality of focus detection zones are arranged in an xe2x80x9cHxe2x80x9d shape, and the autofocus operation can be performed via one focus detection zone selected from the plurality of focus detection zones.
In such a camera provided with a multi-point autofocus system, in addition to an automatic focus-zone selection mode in which a focus detection zone is automatically selected from the plurality of focus detection zones, a manual focus-zone selection mode in which a focus detection zone can be manually selected by the user from the plurality of focus detection zones is generally available.
Conventionally, in such a manual focus-zone selection mode, although each focus detection zone can be selected manually so as to make it possible for the user to photograph pictures which conform to his/her intention, the autofocus operation cannot be performed to stop performing subsequent operations if the calculated amount of defocus is invalid for the focus detection zone selected by the user (i.e., if a valid amount of defocus cannot be obtained at the focus detection zone selected by the user). Therefore, if the calculated amount of defocus for the focus detection zone selected by the user is invalid, the user has to select another focus detection zone, or to do some other operation, which is troublesome.
The present invention has been made in view of the aforementioned problems that reside in conventional multi-point autofocus system, and an object of the present invention is to provide a multi-point autofocus system which has an improvement in manual focus-zone selection mode.
To achieve the object mentioned above, according to an aspect of the present invention, a multi-point autofocus system is provided, including a focus detection device which can calculate a defocus amount for each of a plurality of focus detection zones in a picture plane; a selecting device for manually selecting a focus detection zone from the plurality of focus detection zones for which the defocus amount is to be calculated by the focus detection device; and a determining device for determining a valid focus detection zone by which a valid defocus amount can be calculated out of at least one of the plurality of focus detection zones other than the manually-selected focus detection zone, in such a manner that a higher priority is given to a focus detection zone than another focus detection zone of the plurality of focus detection zones in the case where the result of a calculation of the defocus amount of the manually-selected focus detection zone is invalid.
In an embodiment, the determining device assigns priorities to at least one of the plurality of focus detection zones other than the manually-selected focus detection zone in accordance with an algorithm which gives the higher priority to a focus detection zone which is closer to the manually-selected focus detection zone.
In an embodiment, the determining device assigns priorities to at least one of the plurality of focus detection zones other than the manually-selected focus detection zone in accordance with an algorithm which gives the higher priority to a focus detection zone which is closer to a center of the picture plane.
In an embodiment, the determining device assigns priorities to at least one of the plurality of focus detection zones other than the manually-selected focus detection zone in accordance with an algorithm which gives the higher priority to a focus detection zone which is adjacent to the manually-selected focus detection zone.
In an embodiment, the determining device assigns priorities to at least one of the plurality of focus detection zones other than the manually-selected focus detection zone in accordance with an algorithm which gives the higher priority to a focus detection zone which is closer to the manually-selected focus detection zone, and also closer to the center of the picture plane.
In an embodiment, priorities are determined for each of the plurality of focus detection zones which is manually selected with the selecting device as the manually-selected focus detection zone.
Preferably, the determining device includes a data table which represents priorities, wherein the priorities are assigned to at least one of the plurality of focus detection zones in accordance with the manually-selected focus detection zone.
Preferably, the picture plane has a rectangular shape, and the plurality of focus detection zones includes a central focus detection zone positioned at substantially a center of the picture plane; at least one of left and right focus detection zones which are provided on the picture plane on the left and right sides of the central focus detection zone, respectively; and at least one of upper and lower focus detection zones which are provided on the picture plane on the upper and lower sides of the central focus detection zone, respectively.
In an embodiment, the determining device assigns the priorities to the at least one of the plurality of focus detection zones other than the manually-selected focus detection zone in such a manner that a higher priority is given to the upper focus detection zones in a case where the central focus detection zone is manually selected with the selecting device and where the focus detection device cannot calculate a valid defocus amount for the central focus detection zone which is selected by the selecting device.
In an embodiment, the determining device assigns the priorities to the at least one of the plurality of focus detection zones other than the manually-selected focus detection zone in such a manner that a higher priority is given to the at least one of upper and lower focus detection zones in a case where the central focus detection zone is manually selected with the selecting device and where the focus detection device cannot calculate a valid defocus amount for the central focus detection zone which is selected by the selecting device.
In an embodiment, the multi-point autofocus system further includes an indicator which lights up a first portion on the picture plane corresponding to one of the plurality of focus detection zones which is manually selected with the selecting device.
In an embodiment, the multi-point autofocus system further includes an indicator which lights up a first portion on the picture plane corresponding to one of the plurality of focus detection zones for which the determining device determines that a valid defocus amount can be calculated by the focus detection device.
In an embodiment, the indicator firstly lights up the first portion on the picture plane; and in the case where the focus detection device cannot calculate a valid defocus amount for the manually-selected focus detection zone and the determining device determines that a valid defocus amount can be calculated for one of the plurality of focus detection zones other than the manually-selected focus detection zone, the indicator subsequently lights up a second portion on the picture plane corresponding to the one of the plurality of focus detection zones other than the manually-selected focus detection zone while making the first portion flashing on and off.
In an embodiment, the multi-point autofocus system can be incorporated in a camera, wherein the indicator indicates the first portion in a field of view of a viewfinder of the camera.
In an embodiment, the multi-point autofocus system is incorporated in a camera, wherein the indicator indicates the first and second portions in a field of view of a viewfinder of the camera.
In an embodiment, the multi-point autofocus system is incorporated in a camera, wherein the indicator includes an external display panel provided on a body of the camera. In an embodiment, the multi-point autofocus system is incorporated in a camera having an automatic focus-zone selection mode in which a focus detection zone is automatically selected from the plurality of focus detection zones, and a manual focus-zone selection mode in which a focus detection zone can be manually selected from the plurality of focus detection zones with the selecting device.
In an embodiment, the determining device operates only in the manual focus-zone selection mode.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2000-204278 (filed on Jul. 5, 2000) which is expressly incorporated herein by reference in its entirety.